The present invention is a novel apparatus for cooling fuel for internal combustion engines, as well as cooling the fuel delivery components which are the fuel injectors, carburetors and throttle bodies.
Auto-ignition or pre-ignition diminishes engine performance because excessive pressure or heat inside the cylinder causes the fuel/air mix to fire at inopportune times. See Taylor, Internal Combustion Engine in Theory and Practice, 40-41, 84 (MIT Press Rev. Ed. 1985). One effort to reduce cylinder temperature addressed the concern of auto-ignition by reversing the flow of fluid from the radiator so that the coolest fluid entered the hottest part of the engine block, so as to cool the cylinder walls. See Lumley, Engines: An Introduction, 95-96 (Cambridge Univ. Press: 1999). Cooler fuel/air mix inside the cylinders helps to insure ignition will occur when the spark is delivered by the timing mechanism, thus producing optimal performance within the compression ratio. Cooler fuel than currently available would allow engine timing to be moved closer to top dead center (TDC), thus increasing the power stroke of each piston. Cooler fuel inside the intake manifold also means more oxygen will be present in the fuel/air mix because a cooler gas will be denser, and more oxygen near the ignition spark insures more efficient and rapid oxidation of the fuel inside the cylinder.
The heat under the hood of a car is located (1) in the engine components as it is conducted from the cylinders through the intake manifold and other components in the area and (2) also in the ambient air as it is heated by the engine and environmental conditions. The temperature of the engine components under many environmental conditions can be in the range of 150-250 degrees Fahrenheit. The temperature of the fluid cooling system for the engine (hereinafter called the xe2x80x9cprincipal cooling systemxe2x80x9d) is at least 150 degrees Fahrenheit. Fuel moves slowly enough through the fuel line to allow heat exchange, so fuel will also absorb heat by means of the fuel line itself acting as a heat exchange. Failure to supply enough cooling for the fuel close to the intake manifold means that the injectors, carburetor(s) or throttle bodies which introduce fuel into the intake manifold (collectively referred to herein as xe2x80x9cfuel delivery componentsxe2x80x9d) results in the fuel delivery components acting as a heat exchange for the fuel. Thus, hot fuel delivery components increase the fuel temperature and eliminate the advantage of any efforts to cool the fuel upstream in the fuel system. Providing an excess amount of cooling for the fuel, however, allows the cooled fuel itself to cool the fuel delivery components, thus providing a cooled buffer area for the fuel as it passes into the intake manifold.
Various attempts have been made to improve engine performance by lowering the temperature of fuel entering the cylinders for ignition. These efforts have largely been ineffective because the devices or practices have not delivered enough cooling at the right location, i.e., just prior to entry of the fuel into the fuel delivery components. Previous fuel cooling devices are exemplified in Stay, U.S. Pat. No. 5,558,069 (cooling through compressed gas in a vortex tube); Schmitz, U.S. Pat. No. 5,887,555 (cooling in marine fuel pump to reduce vapor lock); Freeburn, U.S. Pat. No. 4,453,503 (remote thermoelectric unit cooled by air heat sink, xe2x80x9cambientxe2x80x9d fresh or brine water, cascading thermoelectric units, or mechanical refrigeration); Marthaler, U.S. Pat. No. 5,988,265 (fuel cooler core cooled only by principal coolant system for engine block); and others in the above-listed patents. The prior art, however, suffers the disadvantage of lacking several elements of the present invention including, without limitation, a second cooling fluid system comprised of a cooling fluid radiator and cooling fluid pump. Additionally, none of the prior art cools the fuel delivery components to provide an additional buffer of cooling so as to minimize heat re-absorption after initial cooling of the fuel.
The lack of an effective fuel cooling apparatus in the prior art is manifested in part by the existence of various stop-gap methods of fuel cooling among racing enthusiasts such as refrigerating fuel cans with ice. Another indication of the state of the prior art is a device which injects gaseous nitrous oxide into the intake manifold. Nitrous oxide, however, is a drastic form of cooling, and can only be used briefly and in high gears because it produces extreme cooling and a tremendous spike in engine performance. Thus, there is a need for an apparatus to provide a cooling of fuel that improves engine performance consistently in any gear ratio. It would also be advantageous to provide a device that cools the fuel delivery components so as to minimize heat re-absorption prior to fuel entry into the intake manifold.
The present invention satisfies these needs by cooling fuel in a fuel-cooling block of a highly heat-conductive material which allows for maximum heat exchange of fuel with the cold side of a thermoelectric unit using the Peltier effect. The Peltier effect is the separation of heat and cold when current flows through dissimilar conductors. A thermoelectric unit is a sandwich formed by two ceramic plates with an array of small Bismuth Telluride couples in between. After the fuel has been cooled, the fuel then cools the fuel delivery components.
The apparatus contains at least one fuel-cooling block which contains at least one fuel entry port for fuel which is received from the fuel tank and the fuel pump, and also at least one fuel exit port which is coupled to the fuel delivery components, in the case of fuel injectors, by means of at least one fuel injector receptor cup. The fuel-cooling block has an opening on the inside which maximizes the heat exchange with the thermoelectric unit. The apparatus also contains a system for circulating cooling fluid (which is separate and distinct from the principal cooling system for the engine block) containing at least one cooling fluid block with at least one cooling fluid entry port coupled to a cooling fluid pump and to a cooling fluid radiator. The cooling fluid block has an opening on the inside which maximizes the heat exchange with the thermoelectric unit. The cooling fluid block, cooling fluid radiator and cooling fluid pump allow cooling fluid to circulate through the enclosed system. The apparatus contains a thermoelectric unit which has electrical terminals for receiving power from a power supply, a cold side thermally coupled with the fuel-cooling block for heat exchange, and a hot side thermally coupled with the cooling fluid block for heat exchange.
The above apparatus can be embodied so that the system for circulating cooling fluid uses excess fuel as the cooling fluid. The excess fuel is received by the cooling fluid block from the fuel bypass pressure regulator, and returns to the fuel tank where heat is exchanged. A controlled flow of fuel is assured by the fuel pump which pumps fuel from the fuel tank. Also, an additional heat sink can be coupled to the cooling fluid block and to the fuel tank, so as to provide additional cooling for the fuel if necessary.
The apparatus also contains an optional controllable switch to interrupt the power supply to the thermoelectric unit in the event the fuel is cooled to a pre-determined temperature.